The invention relates to an internal energy supply for an energy storage module for an energy storage device and an energy storage device comprising such an energy storage module, in particular in modularly constructed battery direct inverter circuits or battery converter circuits which, for example, are used in electrical drive systems of electrically driven vehicles.
It is becoming apparent that electronic systems, which combine new energy storage technologies with electrical drive engineering, will increasingly be used in the future in stationary applications, such as, e.g., wind power turbines or solar plants, as well as in vehicles, such as hybrid or electric vehicles.
In order to feed three-phase alternating current into an electrical machine, a DC voltage provided by a DC intermediate circuit is conventionally converted into a three-phase alternating voltage by means of an inverter in the form of a pulse width modulated inverter. The DC intermediate circuit is fed by a line consisting of serially connected battery modules. In order to meet the requirements for power and energy that are given for a respective application, a plurality of battery modules is frequently connected in series in a traction battery. Such an energy storage system is, for example, frequently used in electrically driven vehicles.
In the American patent publication U.S. Pat. No. 5,642,275 A1, a battery system having an integrated inverter function is described. Systems of this type are known by the name of multilevel, cascaded inverters or also by the name of battery direct inverters (BDI). Such systems comprise direct current sources in a plurality of energy storage module lines which can be directly connected to an electrical machine of an electrical network. Single-phase or multi-phase supply voltages can thereby be generated. The energy storage module lines comprise a plurality of energy storage modules connected in series, wherein each energy storage module has at least one battery cell and an associated controllable coupling unit which allow said module to interrupt the respective energy storage module or bridge the respectively associated at least one battery cell or to connect said respectively associated at least one battery cell into the respective energy storage module line as a function of control signals.
As an alternative, the German patent publications DE 10 2010 027 857 A1 and DE 10 2010 027 861 A1 disclose modularly interconnected battery cells in energy storage devices which can be selectively coupled into or decoupled from the line consisting of battery cells connected in series via a suitable actuation of coupling units. Systems of this type are known by the name of battery direct converter (BDC). Such systems comprise DC supply sources in an energy storage module line, which DC supply sources can be connected by means of a pulse width modulated inverter to a DC intermediate circuit for the electrical energy supply of an electrical machine or an electrical network.
BDCs and BDIs usually have a higher degree of efficiency and a higher degree of reliability with respect to conventional systems. The reliability is ensured inter alia by virtue of the fact that failed battery cells or cells that are not completely efficient can be disconnected by means of a suitable bridging control of the coupling units from the energy supply lines.
The signal and power electronics for the coupling units of the battery cells can be supplied with current from their own battery cells. An interruption in the series circuit of the battery cells during a charging process can however, for example, be a problem here; thus causing the signal and power electronics to no longer be supplied with current, and therefore a shutdown of the coupling units to no longer be assured. An option to remedy this problem consists of a redundant energy supply of the signal and power electronics by means of external energy sources. This, however, requires additional implementation cost and effort for connecting up the redundant energy source.